How do I traverse a collection in classic ASP? - asp-classic

Question

I want to be able to do:
For Each thing In things
End For
CLASSIC ASP - NOT .NET!

Answer 1

Something like this?
dim cars(2),x
cars(0)="Volvo"
cars(1)="Saab"
cars(2)="BMW"
For Each x in cars
response.write(x & "<br />")
Next
See www.w3schools.com.
If you want to associate keys and values use a dictionary object instead:
Dim objDictionary
Set objDictionary = CreateObject("Scripting.Dictionary")
objDictionary.Add "Name", "Scott"
objDictionary.Add "Age", "20"
if objDictionary.Exists("Name") then
' Do something
else
' Do something else
end if

Answer 2

Whatever your [things] are need to be written outside of VBScript.
In VB6, you can write a Custom Collection class, then you'll need to compile to an ActiveX DLL and register it on your webserver to access it.

Answer 3

The closest you are going to get is using a Dictionary (as mentioned by Pacifika)
Dim objDictionary
Set objDictionary = CreateObject("Scripting.Dictionary")
objDictionary.CompareMode = vbTextCompare 'makes the keys case insensitive'
objDictionary.Add "Name", "Scott"
objDictionary.Add "Age", "20"
But I loop through my dictionaries like a collection
For Each Entry In objDictionary
Response.write objDictionary(Entry) & "<br />"
Next
You can loop through the entire dictionary this way writing out the values which would look like this:
Scott
20
You can also do this
For Each Entry In objDictionary
Response.write Entry & ": " & objDictionary(Entry) & "<br />"
Next
Which would produce
Name: Scott
Age: 20

Answer 4

One approach I've used before is to use a property of the collection that returns an array, which can be iterated over.
Class MyCollection
Public Property Get Items
Items = ReturnItemsAsAnArray()
End Property
...
End Class
Iterate like:
Set things = New MyCollection
For Each thing in things.Items
...
Next

Answer 5

As Brett said, its better to use a vb component to create collections. Dictionary objects are not very commonly used in ASP unless for specific need based applications.

Answer 6

Be VERY carefully on using VB Script Dictionary Object!
Just discover this "autovivication" thing, native on this object: http://en.wikipedia.org/wiki/Autovivification
So, when you need to compare values, NEVER use a boolen comparison like:
If objDic.Item("varName") <> "" Then...
This will automatically add the key "varName" to the dictionary (if it doesn't exist, with an empty value) , in order to carry on evaluating the boolean expression.
If needed, use instead If objDic.Exists("varName").
Just spend a few days knocking walls, with this Microsoft "feature"...
vbscript-dictionary-object-creating-a-key-which-never-existed-but-present-in-another-object